The role of antiplatelet therapy in the secondary prevention of coronary artery disease

Reduce mortality risk above all else: a discrete-choice experiment in acute coronary syndrome patients

BACKGROUND AND OBJECTIVE

Cardiovascular disease is the main cause of death in Germany and other industrialized countries. However, until now, little has been known about how people with acute coronary syndrome (ACS) value aspects of their medical treatment. The objective of this study was to evaluate patients' preferences regarding different antiplatelet medication options following an ACS.

METHOD

After identification of patient-relevant treatment attributes (a literature review and qualitative interviews), a discrete-choice experiment (DCE) including five patient-relevant attributes was conducted. The DCE used a forced-choice approach in which no "opt out" was present, as no treatment is not an option after ACS. The attribute and level combinations were created using a fractional-factorial NGene design with priors. Data analysis was performed using a random-effects logit model. An additional generalized linear latent and mixed models (GLLAMM) analysis was performed to evaluate subgroup differences.

RESULTS

ACS patients (N = 683) participated in computer-assisted personal interviews. Preference analysis showed a clear dominance of the attribute "mortality risk" (coefficient: 0.803). Ranked second was "side effect: dyspnea" (coefficient: 0.550) followed by "risk of a new myocardial infarction" (coefficient: 0.464) and "side effect: bleeding" (coefficient: 0.400). "Frequency of intake" was less important (coefficient: 0.025). Within the 3-class GLLAMM, the variables "marital status" (p = 0.008), "highest level of education" (p = 0.003), and "body-mass index" (according to World Health Organization cluster; p = 0.014) showed a significant impact on the estimated class probabilities.

CONCLUSION

Our study found "mortality risk" to be of the highest value for patients. Patient-centered care and decision making requires consideration of patient preferences; moreover, the information on preferences can be used to develop effective therapies after an ACS. The data generated will enable healthcare decision makers and stakeholders to understand patient preferences to promote patients' benefit.

Platelet reactivity tests for assessing antiplatelet drug response: what the clinician needs to know

Antiplatelet therapy is a cornerstone in the treatment of cardiovascular disease to prevent ischemic events. Various tests have become clinically available to measure platelet function after antiplatelet treatment. A wide interpatient variability in the magnitude of platelet inhibition has been demonstrated in numerous studies, especially in response to clopidogrel. Several reasons including clinical, pharmacological and genetic factors have been identified. High on-clopidogrel platelet reactivity has been linked to adverse clinical outcome, in particular to stent thrombosis after percutaneous coronary interventions. New antiplatelet drugs including prasugrel and ticagrelor have been advocated to overcome the limitations of clopidogrel. Several studies addressed the concept of tailored antiplatelet treatment according to the results of platelet function testing. Within this review, we summarize the current status of personalized antiplatelet therapy for cardiovascular disease.

ADP-induced platelet aggregation and thrombin generation are increased in Essential Thrombocythemia and Polycythemia Vera

INTRODUCTION

Essential Thrombocythemia (ET) and Polycythemia Vera (PV) patients are characterized by an increased rate of thrombotic complications and by several abnormalities of platelets, more pronounced in JAK2V617F positive patients. The aim of this study was to characterize the platelet aggregation as well as the platelet procoagulant potential induced by several different agonists in ET and PV patients.

MATERIALS AND METHODS

Venous blood samples were obtained from 65 ET and 51 PV patients. Whole blood impedance aggregometry was utilized to characterize platelet aggregation induced by collagen, ADP, thrombin receptor activating peptide and arachidonic acid, while the Calibrated Automated Thrombogram (CAT) assay was used to determine the thrombin generation (TG) potential induced by ADP in platelet-rich plasma. CAT assay was also performed in the presence of annexin V to evaluate the contribution of platelet phospholipids to TG.

RESULTS AND CONCLUSIONS

ADP-induced platelet aggregation and TG were significantly increased in ET and PV patients compared to controls. The highest values were observed in JAK2V617F positive patients and in patients on aspirin. In these subjects, annexin V was less effective in inhibiting both basal and ADP-induced TG. This study demonstrates for first time that platelets from ET and PV patients are more responsive to the ADP stimulus, in terms of both increased platelet aggregation, and enhanced TG, particularly in the JAK2V617F positive patients. Our data support the hypothesis that the use of ADP receptor inhibitors, in addition to aspirin, might be considered in the prevention of thrombosis in these conditions, by allowing a more complete inhibition of platelet functions.

Advances in antiplatelet technologies to improve cardiovascular disease morbidity and mortality: a review of ticagrelor

Antiplatelet therapy is widely used with proven benefit for the prevention of further ischemic cardiac complications in patients with acute coronary syndrome. Treatment guidelines for acute coronary syndrome and percutaneous coronary intervention now recommend the use of oral antiplatelet agents including ticagrelor, prasugrel, or clopidogrel in combination with aspirin to comprise dual antiplatelet therapy for the prevention of recurrent ischemic events. The limitations of conventional antiplatelet therapy with clopidogrel or prasugrel include the potential for low response to clopidogrel identified through platelet reactivity or genetic testing, increased risk of bleeding with prasugrel, or slower return to normal platelet activity in patients who received either prasugrel or clopidogrel prior to emergent or planned surgical procedures. This review will discuss the pharmacokinetic and pharmacodynamic properties of ticagrelor in comparison to conventional P2Y12 receptor inhibitors and its utility in patients identified as low responders to clopidogrel. Completed clinical studies and substudies comparing ticagrelor to clopidogrel and ongoing clinical trials evaluating ticagrelor in acute coronary syndrome patients will also be reviewed.

Network meta-analysis of prasugrel, ticagrelor, high- and standard-dose clopidogrel in patients scheduled for percutaneous coronary interventions

Since novel antiplatelet treatments (prasugrel, ticagrelor, high-dose clopidogrel) have been predominantly tested against standard-dose clopidogrel, data on direct comparisons between these therapies are scarce. We therefore indirectly compared their efficacy and safety in patients undergoing percutaneous coronary intervention. Electronic databases were searched systematically to identify head-to-head randomised controlled trials (RCTs). Network meta-analysis was performed using generalised linear mixed models with adjustment for length of follow-up. Findings were corroborated by mixed treatment comparison through Bayesian methods. Fourteen RCTs were identified and included in the analysis (high- vs. standard-dose clopidogrel: 9 trials, prasugrel vs. high-dose clopidogrel: 2 trials, prasugrel vs. standard-dose clopidogrel: 2 trials, ticagrelor vs. standard-dose clopidogrel: 1 trial). No significant differences were found for efficacy outcomes except for stent thrombosis favouring prasugrel (vs. ticagrelor: odds ratio [OR] 0.63, 95% confidence interval [CI]: 0.42, 0.94; vs. high-dose clopidogrel: OR 0.70, 95%CI: 0.48, 1.01). Prasugrel exhibited a similar bleeding risk as high-dose clopidogrel, but more major (OR 1.43, 95%CI 1.07, 1.90) and major or minor bleeding (OR 1.36, 95%CI 1.09, 1.69) compared to ticagrelor. Ticagrelor was also associated with less major or minor bleeding compared to high-dose clopidogrel (OR 0.81, 95%CI 0.69, 0.96). No differences were seen for non CABG-related major bleeding between the three strategies. Results were corroborated in a subgroup analysis comprising only patients with acute coronary syndromes. In the absence of head-to-head clinical trials, network meta-analysis suggests potentially relevant differences in efficacy and bleeding risk among novel antiplatelet treatments and may thereby advance understanding of their differential therapeutic properties.

Extracellular nucleotides inhibit insulin receptor signaling, stimulate autophagy and control lipoprotein secretion

Hyperglycemia is associated with abnormal plasma lipoprotein metabolism and with an elevation in circulating nucleotide levels. We evaluated how extracellular nucleotides may act to perturb hepatic lipoprotein secretion. Adenosine diphosphate (ADP) (>10 µM) acts like a proteasomal inhibitor to stimulate apoB100 secretion and inhibit apoA-I secretion from human liver cells at 4 h and 24 h. ADP blocks apoA-I secretion by stimulating autophagy. The nucleotide increases cellular levels of the autophagosome marker, LC3-II, and increases co-localization of LC3 with apoA-I in punctate autophagosomes. ADP affects autophagy and apoA-I secretion through P2Y₁₃. Overexpression of P2Y₁₃ increases cellular LC3-II levels by ∼50% and blocks induction of apoA-I secretion. Conversely, a siRNA-induced reduction in P2Y₁₃ protein expression of 50% causes a similar reduction in cellular LC3-II levels and a 3-fold stimulation in apoA-I secretion. P2Y₁₃ gene silencing blocks the effects of ADP on autophagy and apoA-I secretion. A reduction in P2Y₁₃ expression suppresses ERK1/2 phosphorylation, increases the phosphorylation of IR-β and protein kinase B (Akt) >3-fold, and blocks the inhibition of Akt phosphorylation by TNFα and ADP. Conversely, increasing P2Y₁₃ expression significantly inhibits insulin-induced phosphorylation of insulin receptor (IR-β) and Akt, similar to that observed after treatment with ADP. Nucleotides therefore act through P2Y₁₃, ERK1/2 and insulin receptor signaling to stimulate autophagy and affect hepatic lipoprotein secretion.

Do aspirin and other antiplatelet drugs reduce the mortality in critically ill patients?

Platelet activation has been implicated in microvascular thrombosis and organ failure in critically ill patients. In the first part the present paper summarises important data on the role of platelets in systemic inflammation and sepsis as well as on the beneficial effects of antiplatelet drugs in animal models of sepsis. In the second part the data of retrospective and prospective observational clinical studies on the effect of aspirin and other antiplatelet drugs in critically ill patients are reviewed. All of these studies have shown that aspirin and other antiplatelet drugs may reduce organ failure and mortality in these patients, even in case of high bleeding risk. From the data reviewed here interventional prospective trials are needed to test whether aspirin and other antiplatelet drugs might offer a novel therapeutic option to prevent organ failure in critically ill patients.

Clinical value of antiplatelet therapy in patients with acute coronary syndromes and in percutaneous coronary intervention

Dual antiplatelet therapy with aspirin and clopidogrel is recommended in all patients who have had an acute coronary syndrome or who undergo percutaneous coronary intervention to prevent further ischemic events. Resistance or reduced responsiveness to aspirin and/or clopidogrel has been associated with adverse cardiovascular outcomes, including stent thrombosis. There have been significant advances in this field, which aim to overcome antiplatelet resistance, including the development of new antiplatelet agents. The rationale for dual antiplatelet therapy, the impact of suboptimal efficacy and the potential ways of overcoming resistance or variability in response to antiplatelet agents will be reviewed in this article.